Method and apparatus for transmitting data

ABSTRACT

Provided is a pre-5 th -Generation (5g) or 5G communication system for supporting higher data rates Beyond 4 th -Generation (4g) communication system such as Long Term Evolution (LTE). The present disclosure provides a method performed by a base station in a wireless communication system. The method includes determining at least one energy detection threshold for sensing based on a signal to be transmitted; identifying a detected power corresponding to a channel of an unlicensed band; determining whether the channel is idle based on the detected power and the at least one energy detection threshold; and transmitting the signal to a user equipment (UE) on the channel based on a determination that the channel is idle. The at least one energy detection threshold corresponds to the signal to be transmitted including a first signal or a second signal, and the second signal includes at least one discovery signal, and the first signal is different from the second signal.

PRIORITY

The application is a Continuation Application of U.S. patent applicationSer. No. 16/731,463, filed in the U.S. Patent and Trademark Office(USPTO) on Dec. 31, 2019, which is a Continuation Application of U.S.patent application Ser. No. 15/525,132, filed in the USPTO on May 8,2017, issued as U.S. Pat. No. 10,616,922 on Apr. 7, 2020, which is aNational Phase Entry of International Patent Application No.PCT/KR2015/011989, which was filed on Nov. 9, 2015, and claims priorityto Chinese Patent Applications No. 201410643819.X, 201410785114.1, and201510163387.7, which were filed on Nov. 7, 2014, Dec. 17, 2014, andApr. 8, 2015, respectively, the entire content of each of which isincorporated herein by reference.

BACKGROUND 1. Field

The present disclosure relates to wireless communication techniques, andmore particularly, to a method and apparatus for transmitting data on anunlicensed band based on a Long-Term Evolution (LTE) system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4G (4th-Generation) communication systems, efforts havebeen made to develop an improved 5G (5th-Generation) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘beyond 4G network’ or a ‘post LTE system’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud radioaccess networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, coordinated multi-points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, hybrid FSK and QAM modulation (FQAM) and slidingwindow superposition coding (SWSC) as an advanced coding modulation(ACM), and filter bank multi carrier (FBMC), non-orthogonal multipleaccess (NOMA), and sparse code multiple access (SCMA) as an advancedaccess technology have been developed.

Long-Term Evolution (LTE) system of 3rd Generation Partnership Project(3GPP) supports two duplex modes including Frequency Division Duplex(FDD) and Time Division Duplex (TDD).

As shown in FIG. 1 which shows an existing FDD radio frame structure,for the FDD system, each radio frame is of 10 ms length, consists of ten1 ms subframes. Each subframe consists of two consecutive 0.5 ms slots,i.e., the kth subframe includes slot 2k and slot 2k+1, k=0, 1, . . . ,9.

As shown in FIG. 2 which shows an existing TDD radio frame structure,for the TDD system, each 10 ms radio frame is divided into two 5 mshalf-frames. Each half-frame includes eight 0.5 ms subframes and threespecial fields, i.e., downlink pilot slot (DwPTS), guard period (GP) anduplink pilot slot (UpPTS). The total length of the three special fieldsis 1 ms. Each subframe consists of two consecutive slots, i.e., the kthsubframe includes slots 2k and slot 2k+1, k=0, 1, . . . , 9. Onedownlink Transmission Time Interval (TTI) is defined in one subframe.

When the TDD radio frame is configured, 7 kinds of uplink-downlinkconfigurations are supported, as shown in Table 1. Herein, D denotesdownlink subframe, U denotes uplink subframe, and S denotes a specialsubframe including the above three special fields.

Table 1 uplink-downlink configurations of LTE TDD.

TABLE 1 Switching Configuration point Subframe index index periodicity 01 2 3 4 5 6 7 8 9 0  5 ms D S U U U D S U U U 1  5 ms D S U U D D S U UD 2  5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms D S UU D D D D D D 5 10 ms D S U D D D D D U D 6 10 ms D S U U U D S U U D

First n Orthogonal Frequency Division Multiplexing (OFDM) symbols ofeach downlink subframe may be used for transmitting downlink controlinformation. The downlink control information includes Physical DownlinkControl Channel (PDCCH) and other control information, wherein n=0, 1,2, 3 or 4; remaining OFDM symbols may be used for transmitting PhysicalDownlink Shared Channel (PDSCH) or Enhanced PDCCH (EPDCCH). In the LTEsystem, PDCCH and EPDCCH are used for bearing Downlink ControlInformation (DCI) allocating uplink channel resources or downlinkchannel resources, respectively referred to as Downlink Grant (DL Grant)and Uplink Grant (UP Grant). In the LTE system, the DCI of different UEsare transmitted independently, and the DL Grant and the UL Grant arealso transmitted independently.

In enhanced system of the LTE system, a wider working bandwidth isobtained through combining multiple Component Carriers (CC), i.e.,Carrier Aggregation (CA), to form downlink and uplink of thecommunication system and therefore support higher transmission rate.Herein, the aggregated CCs may have the same duplex mode, e.g., all ofthem are FDD cells or TDD cells. The aggregated CCs may also havedifferent duplex modes, i.e., there exist FDD cells and TDD cells at thesame time. For one UE, a base station may configure it to work inmultiple cells, one of them is a primary cell (PCell) and others aresecondary cells (SCell). For the LTE CA system, transmission of theHybrid Automatic Repeat Request-Acknowledgement (HARQ-ACK) and ChannelState Information (CSI) on the Physical Uplink Control Channel (PUCCH)are only implemented on the Pcell.

The above LTE system is usually deployed on a licensed band, so as toavoid interferences from other systems. Besides the licensed band, thereare also unlicensed bands. The unlicensed bands generally have beenallocated for other usages, e.g., radar system and/or 802.11 series WiFisystem. The 802.11 series WiFi system operates based on Carrier SenseMultiple Access with Collision Avoidance (CSMA/CA). Before transmittingsignals, a Station (STA) needs to sense the wireless channel. Thewireless channel can be occupied for transmitting signals only when ithas been idle for a specified time period. The STA may determine thestatus of the wireless channel according to two mechanisms inassociation. On the one hand, the STA may practically sense the wirelesschannel using the carrier sensing technique. If signals of another STAare detected or perceived signal power is higher than a predefinedthreshold, it is determined that the wireless channel is busy. At thistime, a physical layer module of the STA may report a Clear ChannelAssessment (CCA) report to a higher layer module indicating that thewireless channel is busy. On the other hand, a virtual carrier sensingtechnique is also introduced in the 802.11 series WiFi system, i.e.Network Allocation Vector (NAV). Each 802.11 frame includes a durationfield. The STA may determine whether it can transmit signal in thewireless channel according to a NAV value in the duration field, whereinthe NAV indicates the amount of time that the wireless channel needs tobe reserved.

For the LTE system, in order to meet the increasing demand of the mobilecommunication services, more spectrum resources need to be explored. Onepossible solution is to deploy the LTE system on the unlicensed band.Since the unlicensed band have generally been allocated for otherusages, the interference level may be unpredictable when the LTE systemis deployed on the unlicensed band, which makes it difficult to ensureQuality of Service (QoS) of data transmission of the LTE system. But theunlicensed band still can be used for data transmission with low QoSrequirement. In this situation, how to avoid the interference to the LTEsystem on the unlicensed band has become an urgent problem to be solved.

SUMMARY

The present disclosure provides a method and an apparatus fortransmitting data on a unlicensed band based on a Long-Term Evolution(LTE) system, so as to control a transmission power of an equipment onthe unlicensed band, increase channel seizing opportunity and ensureeffective coexistence.

A method for transmitting data provided by the present disclosureincludes: performing, by a base station, clear channel assessment (CCA)in a channel of a unlicensed band; determining, by the base station,whether the channel being occupied according to a CCA measurement valuein the channel; and determining, by the base station, a datatransmission parameter based on the whether the channel being occupied.

In one embodiment, the determining the data transmission parameterfurther comprises: taking obtaining the CCA measurement value as a firstCCA threshold level; and obtaining a maximum transmission power allowedduring a next channel occupancy time according to a relationship betweenthe CCA measurement value and the maximum transmission power.

In one embodiment, the determining whether the channel being occupiedfurther comprises: the allowed maximum transmission power by comparingthe CCA measurement value with a second CCA threshold.

In one embodiment, the performing the CCA further comprises: performing,by the base station, a CCA check; and recording, by the base station,CCA measurement values, and wherein the determining the datatransmission parameter further comprises: obtaining a maximum valueamong N smallest CCA measurement values as a first CCA threshold levelaccording to the recorded CCA measurement values, and obtaining amaximum transmission power allowed during a next channel occupancy timeaccording to a relationship between the first CCA threshold level andthe maximum transmission power.

In one embodiment, performing the CCA further comprise: if the CCAmeasurement value is equal to or higher than a second CCA thresholdlevel, not recording the CCA measurement value.

In one embodiment, the performing the CCA further comprises: detectingCCA measurement values of at least two types of signals, wherein thedetermining the data transmission parameter further comprises: obtainingthe CCA measurement value of each type of signals as a first CCAthreshold level, and determining an allowed maximum transmission poweraccording to a relationship between the first CCA threshold value andthe maximum transmission power, wherein the maximum transmission poweris a minimum value of the allowed maximum transmission powers of the atleast two types of signals.

In one embodiment, the CCA measurement values of the at least two typesof signals further comprise: an energy density of recognizable signalsfrom an communication system and an energy density of other signals; orthe CCA measurement values of the at least two types of signalscomprise: energy of recognizable signals from an communication system ofthe same operator with the base station, energy of recognizable signalsfrom an communication system of an operator different from the basestation, and energy of other signals.

In one embodiment, the allowed maximum transmission power is, a maximumvalue of transmission powers on orthogonal frequency divisionmultiplexing (OFDM) symbols or single carrier frequency divisionmultiple access (SCFDMA) symbols in the channel occupancy time; or tomaximum value of average transmission powers of subframes in the channeloccupancy time; or a maximum value of an instant transmission power inthe channel occupancy time.

In one embodiment, if the CCA measurement value is lower than a CCAthreshold value, occupying, by the base station, the channel to transmitthe signals of a type, wherein the CCA threshold level is determinedaccording to the type of signals to be transmitted in the channel.

In one embodiment, data transmission parameter comprise a transmissionpower on each OFDM symbol or an average transmission power of eachsubframe, and wherein the transmission power on each OFDM symbol isunchanged or decreases with time, in one channel occupancy time; orwherein the average transmission power of each subframe is unchanged ordecreases with time, in one channel occupancy time.

In one embodiment, wherein the transmission powers on OFDM symbols inone subframe have a difference within a configured first range.

In one embodiment, average transmission powers of subframes have adifference within a configured second range.

In one embodiment, the method further includes: obtaining a powerboosting proportion of a physical downlink shared channel (PDSCH) inOFDM symbols containing zero power channel state indication-referencesignal (ZP CSI-RS) according to a configuration of higher layersignaling; or calculating, by a UE, a power boosting proportion of aPDSCH on physical resource blocks (PRBs) allocated to the UE accordingto a ZP CSI-RS configuration.

In one embodiment, the method further includes: transmitting, by thebase station, dummy signals.

In one embodiment, Energy Per Resource Element EPRE of the dummy signalsis equal to or lower than a minimum EPRE on effective PRBs.

In one embodiment, in one PRB pair containing the dummy signals, aDemodulation Reference Signal DMRS sequence is defined in advance orconfigured to a Network-Assisted Interference Cancelation andSuppression NAICSUE via higher layer signaling.

In one embodiment, if dedicated DMRS is configured for the dummysignals, n_(scid) is an integer except for 0, 1 and 2.

In one embodiment, in one PRB pair containing the dummy signals, aQuarter Phase Shift Keying QPSK modulation manner is adopted for dataResource Elements REs of the PDSCH, wherein QPSK modulation symbol bornby each RE is random; or a known QPSK sequence is transmitted on each REof the PRB.

In one embodiment, in one PRB pair containing the dummy signals, thedummy signals of a single antenna port are transmitted.

In one embodiment, for a transmission mode based on Cell-specificReference Signal CRS, a preceding matrix of the dummy signals is definedin advance or configured by higher layer signaling.

In one embodiment, for a transmission mode based on CRS, the dummysignals are transmitted using a minimum power control parameter PA,wherein the PA is defined in advance or configured by higher layersignaling.

The present disclosure further provides a base station for transmittingdata, including: a transmitter configured to transmit the data; and atleast one processor configured to: perform a CCA in one channel of aunlicensed band, and determine whether the channel being occupiedaccording to a CCA measurement value in the channel, and determine adata transmission parameter based on the whether the channel beingoccupied.

In one embodiment, at least one processor further configured to: obtainthe CCA measurement value as a first CCA threshold level, and obtain amaximum transmission power allowed during a next channel occupancy timeaccording to a relationship between the CCA measurement value and themaximum transmission power.

In one embodiment, at least one processor further configured to:calculate the allowed maximum transmission power by comparing the CCAmeasurement value with a second CCA threshold.

In one embodiment, at least one processor further configured to: performa CCA check, and record CCA measurement values, and obtain a maximumvalue among N smallest CCA measurement values as a first CCA thresholdlevel according to the recorded CCA measurement values, and obtain amaximum transmission power allowed during a next channel occupancy timeaccording to a relationship between the first CCA threshold level andthe maximum transmission power.

In one embodiment, at least one processor further configured to: if theCCA measurement value is equal to or higher than a second CCA thresholdlevel, not record the CCA measurement value.

In one embodiment, at least one processor further configured to: detectCCA measurement values of at least two types of signals, and obtain theCCA measurement value of each type of signals as a first CCA thresholdlevel, and determine an allowed maximum transmission power according toa relationship between the first CCA threshold value and the maximumtransmission power, wherein the maximum transmission power is a minimumvalue of the allowed maximum transmission powers of the at least twotypes of signals.

In view of the above technical solution, in the method and apparatus fortransmitting data provided by the present disclosure, the LTE equipmentperforms a CCA in the channel of the unlicensed hand, and determineswhether the channel can be occupied according to a CCA measurement valuein the channel, and determines a data transmission parameter if it isdetermined that the channel can be occupied. Thus, the transmissionpower of the equipment can be controlled on the unlicensed band, thechannel seizing opportunity is increased and the effective coexistenceis ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a schematic diagram illustrating an LTE FDD frame structureaccording to the prior art;

FIG. 2 is a schematic diagram illustrating an LTE TDD frame structureaccording to the prior art;

FIG. 3 is a flowchart illustrating a method for transmitting data on theunlicensed band by an LTE equipment according to an embodiment of thepresent disclosure;

FIG. 4 is a flowchart illustrating a first method for determining anallowed maximum transmission power according to an embodiment of thepresent disclosure;

FIG. 5 is a flowchart illustrating a second method for determining theallowed maximum transmission power according to embodiment of thepresent disclosure;

FIG. 6 is a schematic diagram illustrating a process of determining theallowed maximum transmission power according to multiple CCA measurementvalues according to an embodiment of the present disclosure;

FIG. 7 is a first schematic diagram illustrating transmission powerduring one channel occupation time according to an embodiment of thepresent disclosure;

FIG. 8 is a second schematic diagram illustrating the transmission powerduring one channel occupation time according to an embodiment of thepresent disclosure; and

FIG. 9 is a schematic diagram illustrating a structure of an apparatusfor transmitting data according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

The present disclosure is described in further detail hereinafter withreference to accompanying drawings and embodiments to make theobjective, technical solution and merits therein clearer.

On the unlicensed band, other wireless communication system may bedeployed, e.g. radar, WiFi, etc. Therefore, when deploying the LTEsystem on the unlicensed band, interferences between the LTE system andthe above other wireless system should be avoided. In order to avoid theinterferences with other LTE equipment or equipment of the otherwireless system, the LTE equipment shall observe the status of thechannel prior to transmit signals. The channel can only be occupied fordata transmission when it is idle. For facilitating the description, theLTE equipment hereinafter refers to a base station or a LTE in the LTEsystem. On the unlicensed band, the interferences from the otherwireless communication system are out of control. Therefore, it is hardto ensure the QoS. In the present disclosure, the UE may operate in theCA mode, wherein the PCell of the UE is a cell on the licensed band andused for ensuring the QoS of the UE.

FIG. 3 is a flowchart illustrating a method for transmitting data on anunlicensed band by an LTE equipment according to an embodiment of thepresent disclosure. The method includes the following.

At block 301, the LTE equipment performs a Clear Channel Assessment(CCA) in a channel of the unlicensed band.

The CCA may include measuring a signal total energy in the channel. Or,when the LTE equipment is able to recognize a particular signalsequence, the CCA may include measuring the energy of the signalsequence in the channel. The above signal sequence may identify signalsfrom one wireless system. The LTE equipment may obtain statusinformation about signals of multiple wireless systems utilizing theCCA, so as to implement subsequent data transmission according todetected signal type.

At block 302, the LTE equipment determines whether the channel can beoccupied according to a CCA measurement value in the channel, anddetermines a data transmission parameter if the channel can be occupied.

Herein, since the LTE system adopts fixed frame structure, i.e., eachsubframe is of 1 ms length and has fixed start timing and end timing,whereas the time when the LTE equipment finds that the channel is idleis uncertain, the LTE equipment may need to transmit a signal used foroccupying the channel before starting the data transmission, which isreferred to as a preamble hereinafter. Besides occupying the channel,the preamble may have other functions, e.g., Automatic Gain Control(AGC), etc. If the LTE equipment does not transmit any signal before thetiming position for transmitting data, the channel may be seized byother equipment on the unlicensed band.

Hereinafter the technical solution of the present disclosure isdescribed in detail with reference to six embodiments.

Embodiment 1

On the unlicensed band, the equipment firstly detects the channelstatus, i.e., performs a CCA check. The channel can only be occupiedwhen it is detected that the channel is idle or it has been detected fora certain number (the number may be random) of times that the channel isidle according to a further requirement. Herein, when a CCA measurementvalue is lower than a CCA threshold level, it may be regarded that thechannel is idle; otherwise, it is regarded that the channel is occupied.If the requirement for occupying the channel is met, the channeloccupancy time of the equipment may include one or more subframes.

According to European Regulations about the unlicensed band, there is arelationship between the CCA threshold level and a maximum transmissionpower PH of the equipment. example, suppose that a receive antenna gainis 0 dBi, for a 23 dBm equivalent isotropically radiated power (e.i.r.p)transmitter, the CCA threshold level is −73 dBm/MHz. For other transmitpower classes, suppose that the receive antenna gain is 0 dBi, the CCAthreshold level is calculated using TL=−73 dBm/MHz+23−PR According tothe above formula, given the maximum transmission power, the CCAthreshold level required by the Regulations may be derived. Or, giventhe CCA threshold level, the maximum transmission power allowed by theRegulations may be derived.

The LTE system supports uplink and downlink transmission power control,thus the transmission power of the base station and the UE are bothadjustable. In particular:

For the downlink transmission of the LTE system, the eNB may control itsdownlink transmission power according to the channel status of each UE.For example, for transmission modes 1˜6, the transmission power withrespect to one UE may be controlled via semi-statically configuredparameters PA and PB. For transmission modes 7˜9, the downlinktransmission power with respect to one UE may be adjusted dynamicallysince the data demodulation is based on DMRS. Since different UEs may bescheduled by the eNB in different downlink subframes, the totaltransmission power of different downlink subframes are generallydifferent. Further, inside one subframe, different time-frequencyresources may bear different types of information, therefore thetransmission power of different OFDM symbols may also be different. Forexample, the transmission power of OFDM symbols where CRS exist and thetransmission power of other OFDM symbols may be different. Thetransmission power of OFDM symbols where Zero Power Channel StateIndication-Reference Signal (ZP CSI-RS) is applied and the transmissionpower of other OFDM symbols are also different. In view of the above,during one channel occupancy time period, the downlink transmissionpower of the LTE base station generally varies in different subframes orinside one subframe. In addition, for different channel occupancy timeperiods, the downlink transmission power of the LTE base station is alsodifferent.

For the uplink transmission of the LTE system, the LTE may activelyadjust the transmission power via open-loop power control, and the basestation may control the transmission power of the UE via close-looppower control. In addition, in case that the power is restricted, theLTE may adjust the transmission power of a component carrier accordingto a certain criteria. In one uplink subframe, the transmission power ofthe UE is also variable, e.g., PUSCH is transmitted at the start of theuplink subframe and SRS is transmitted on the last symbol. Thus, theuplink transmission power of the UE is also adjustable.

As described above, in one channel occupancy time period, thetransmission power of the LTE equipment is fluctuate. And in differentchannel occupancy time periods, the transmission power of the LTEequipment may also be different. In the present disclosure, it isdefined that a maximum transmission power is a maximum value of thetransmission power in one channel occupancy time period. During onechannel observation of the LTE equipment, the CCA measurement value istaken as a first CCA threshold level, and a current allowed maximumtransmission power is obtained according to the relationship between thefirst CCA threshold level and the maximum transmission power. The abovemaximum transmission power may be a signal total power inputted by theequipment to the antenna, i.e., not including the antenna gain; or themaximum transmission power may refer to the e.i.r.p of the antenna,i.e., including the antenna gain.

For example, the maximum value of the transmission power is denoted byPH, the first CCA threshold level is TL, and the CCA measurement valueis denoted by E. Thus, according to E=TL<=−73 dBm/MHz+23−PH, it may beobtained that PH=−73 dBm/MHz+23−E. The above maximum value of thetransmission power may be the maximum value among the transmissionpowers of the OFDM symbols or SCFDMA symbols during channel occupancytime of the equipment, or a maximum value among average transmissionpowers of subframes of the equipment during the channel occupancy time,or a maximum value of an instant transmission power of the equipmentduring the channel occupancy time.

According to the above method, it is possible to calculate an allowedmaximum transmission power corresponding to each CCA measurement value,and allow the equipment to occupy the channel with a transmission powernot exceeding the allowed maximum transmission power. Or, the abovemethod may be used to determine the allowed maximum transmission poweronly when the CCA measurement value is lower than a second CCA thresholdlevel TL2, i.e., when the CCA measurement value is lower than TL2. Atthis time, the equipment can occupy the channel but the restriction ofthe allowed maximum transmission power must be complied with. When theCCA measurement value is equal to or higher than TL2, the equipmentcannot occupy the channel. Herein, TL2 is the maximum value of the CCAmeasurement value that the channel is allowed to be occupied. Or, theabove method may be used to determine the allowed maximum transmissionpower only when the CCA measurement value is higher than a third CCAthreshold level TL3, i.e., when the CCA measurement value is higher thanTL3. At this time, the equipment can occupy the channel but therestriction of the allowed maximum transmission power must be compliedwith. When the CCA measurement value is equal to or lower than TL3, themaximum transmission power is subject to the threshold TL3 and cannotexceed it. Herein, TL3 is to control the maximum transmission power thatthe equipment can use. Or, the thresholds TL2 and TL3 may be configuredat the same time, and. TL2>TL3, i.e., only when the CCA measurementvalue is lower than TL2 but higher than TL3, it is possible to determinethe allowed maximum transmission power according to the above method.When the CCA measurement value is equal to or higher than TL2, theequipment cannot occupy the channel. When the CCA measurement value isequal to or lower than TL3, the maximum transmission power of theequipment is subject to threshold TL3 and cannot exceed it.

Suppose that the CCA check mechanism is: once it is found that thechannel is idle, the equipment may occupy the channel. For example,according to the European Regulations, for a Frame Based Equipment(FBE), the channel status is observed at the start of each frame period,if the CCA Observation indicates that the channel is idle, the equipmentmay occupy the channel during a next frame period. If the channel isoccupied, the equipment cannot occupy the channel during a next frameperiod. As shown in FIG. 4, according to the above method, the maximumtransmission power can be used by the equipment during the next frameperiod may be obtained according to the current CCA measurement value.According to this method, the equipment may further determine whetherthe allowed maximum transmission power meets its scheduling requirement.If it meets the scheduling requirement, the equipment occupies thechannel and keeps its transmission power not exceeding the above allowedmaximum transmission power. If it does not meet the schedulingrequirement, the equipment may give up the occupation. For example, ifthe allowed maximum transmission power is relatively low, the basestation may consider scheduling a UE with a better channel condition.For the uplink transmission of the UE, the UE may consider the impact ofdecreasing uplink transmission power.

Suppose that the CCA detect scheme is: if it has been detected for acertain number of times N (e.g., N is a random number) that the channelis idle, the equipment may occupy the channel. For example, according tothe European Regulations, a Load Based Equipment (LBE) starts to observethe channel when it has a data transmission requirement. If the CCAcheck indicates that the channel is occupied, a random number N isgenerated and the equipment keeps on observing the channel. After Ntimes of channel idle are observed, the channel can be occupied.Generally, when the equipment observes the channel, the CCA measurementvalue during each observation is different. Therefore, the allowedmaximum transmission power obtained according to the CCA measurementvalue following the above method may also be different.

As shown in FIG. 5, in order to determine the maximum transmission powercan be used by the equipment when occupying the channel, one method isto record each CCA measurement value and determine the allowed maximumtransmission power according to a maximum value among N smallest CCAmeasurement values. Or, the equipment may only record N smallest CCAmeasurement values after it starts to observe the channel. Inparticular, after the equipment finishes a new CCA measurement, if thenew CCA measurement value is larger than or equal to a maximum value ofthe above N smallest CCA measurement values, the new CCA measurementvalue is discarded. If the new CCA measurement value is smaller than themaximum value of the above N smallest CCA measurement values, themaximum value of the above N smallest CCA measurement values isdiscarded and the new CCA measurement value is recorded. The equipmentmay determine the allowed maximum transmission power according to amaximum value of the above N smallest CCA measurement values. If theallowed maximum transmission power is able to meet a data transmissionrequirement, the equipment occupies the channel and keeps itstransmission power not exceeding the allowed maximum transmission power;otherwise the equipment may keep on with the CCA check of the channeluntil an allowed maximum transmission power determined according to themaximum value of the N smallest CCA measurement values is able to meetthe data transmission requirement. According to the above method, if theabove threshold TL2 is defined and the CCA measurement value is equal toor larger than TL2, the LTE may directly proceed with subsequent CCAcheck instead of recording the CCA measurement value.

Or, the equipment may obtain a fourth CCA threshold level TL4 currentlyto be used according to a required maximum transmission power and therelationship between the maximum transmission power and the CCAthreshold level. Thereafter, during the CCA check procedure, TL4 may betaken as a CCA threshold level to observe the channel. If the CCAindicates that the channel has been idle for N times, the equipment mayoccupy the channel and keeps its transmission power not exceeding themaximum transmission power used for determining the CCA threshold level.

Embodiment 2

On one channel of the unlicensed band, there may already exist signalsof other LTE cells and/or other wireless systems. Therefore, whendetermining whether the channel can be occupied, an LTE equipment has toconsider impact to the other LTE cells and/or other wireless systems andmay adopt different processing manners with respect to the signals ofother LTE cells and signals of other wireless systems. For example,different CCA threshold levels may be used with regard to differenttypes of signals. The CCA measurement values of the different types ofsignals are denoted by E_(k). For example, it is possible todifferentiate energy densities E₀ and E₁ of the recognizable signalsfrom the LTE system and the other signals; or, it is possible todifferentiate energy densities E₀, E₁ and E₂ of the recognizable signalsfrom the LTE system of the same operator, the recognizable signals fromthe LTE system of a different operator and other signals.

The method of embodiment 1 may be adopted to detect the CCA measurementvalues of the signals of different types. For each type of signals, anallowed maximum transmission power within the corresponding channeloccupancy time may be determined according to its CCA measurement value.For example, for a CCA measurement value E_(k) of a type of signals, thecorresponding allowed maximum transmission power PH_(k) is obtainedusing PH_(k)=−73 dBm/MHz+23−E_(k). Thus, multiple allowed maximumtransmission powers may be obtained with regards to the multiple typesof signals. Thus, the maximum transmission power actually used by theequipment during the channel occupancy time may be a minimum value amongthe maximum transmission powers PH_(k) corresponding to the multipletypes of signals, i.e., min(PH₀, . . . , PH_(k)).

For example, for the signals from the LTE system, the allowed maximumtransmission power PH₀ of the LTE equipment may be obtained throughtaking the CCA measurement value E₀ as the CCA threshold level. Forother signals, the allowed maximum transmission power PH₁ of the LTEequipment may be obtained through taking the CCA measurement value ofthe other signals as the CCA threshold level. Thus, the maximumtransmission power that the UM equipment may actually use may be theminimum value of the above two maximum transmission powers, i.e.,min(PH₀, PH₁).

For the signals from the LTE system of the same operator, the allowedmaximum transmission power PH₀ of the LTE equipment may be obtainedthrough taking the CCA measurement value E₀ of the signals as the CCAthreshold level. For signals from an LTE system of another operator, themaximum transmission power PH₁ of the LTE equipment may be obtainedthrough taking the CCA measurement value E₁ as the CCA threshold level.For signals from other systems, the allowed maximum transmission powerPH₂ of the LTE equipment may be obtained through taking the CCAmeasurement value E₂ as the CCA threshold level. Thus, the maximumtransmission power that the LTE equipment may actually use may be aminimum value of the above three maximum transmission powers, i.e.,min(PH₀, PH₂).

Embodiment 3

On the unlicensed band, different functions may be implemented duringone channel occupancy time period. Accordingly, the signals transmittedby the equipment may be different. Hereinafter, signals can betransmitted by the equipment during the channel occupancy time aredescribed. The present disclosure is not limited to the followingsignals.

When the channel is occupied, the base station may transmit downlinkdata. According to the channel status and service condition of the UEcurrently being scheduled, the base station may need to transmit signalsusing a relatively high transmission power or even the maximumtransmission power. Suppose that the base station still needs totransmit Discovery Reference Signal (DRS) on the unlicensed band tosupport PAM measurement of the UE. During one channel occupancy timeperiod, if there is no downlink service, the base station may transmitmerely the DRS. Herein functions of the DRS may be extended to supportCSI measurement. In addition, on the unlicensed band, if signalsdedicated for the CSI measurement are required to be transmitted, e.g.Non-Zero Power Channel State Indication-Reference Signal (NZP CST-RS)signals which are transmitted to support channel measurement of the UE,the base station may transmit merely the NZP CSI-RS during the channeloccupancy time if there is no downlink service. Both the DRS and the NZPCSI-RS do not occupy all subcarriers of the OFDM symbols. Therefore, therequired transmission power is usually lower than the maximumtransmission power of the base station. In the uplink direction, duringone channel occupancy time period, the signals transmitted by the UE maybe any one or any combination of uplink data (PUSCH), Sounding ReferenceSignal (SRS), Physical Random Access Channel (PRACH) signals and PUCCHwhich is used for feeding back Uplink Control information (UCI), etc.When the UE needs to transmit uplink data, the UE may need to use arelatively high transmission power or even the maximum transmissionpower. When the UE does not transmit data, the actually requiredtransmission power may be relatively low.

On the unlicensed band, the equipment has to detect the channel statusfirstly, i.e., performs the CCA check. The channel can be occupied bythe equipment only when it is detected that the channel is idle or ithas been detected for a certain number of times (the number may be arandom number) that the channel is idle according to a furtherrequirement. According to the method of embodiment 1, a certainrelationship has to be met between the CCA threshold level and themaximum transmission power during the channel occupancy time, thusdifferent CCA threshold levels may be adopted in different channeloccupancy time periods and different maximum transmission powers may beused accordingly. According to the above analysis, on the unlicensedband, different functions may be implemented in different channeloccupancy time periods and signals of different types may be transmittedby the equipment. In addition, the transmission power required bydifferent types of signals may also be different. In the presentdisclosure, the CCA threshold level to be adopted may be determinedaccording to the type of signals to be transmitted during the channeloccupancy time. Thus, when the CCA measurement value is lower than theCCA threshold level, the equipment may occupy the channel and transmitthe signals of the corresponding type. In particular, during one channeloccupancy time, the signals transmitted by the equipment may beclassified into N types according to the functions to be implemented,wherein N is larger than 1. For the kth type of signals, the CCAthreshold level is configured as TL_(k), wherein k=1, 2, . . . , N.There exists a relationship between the CCA threshold levelcorresponding to one type of signals and the transmission power to beadopted. For example, the maximum transmission power of a type ofsignals is denoted by PH_(k), the CCA threshold level is TL_(k), the CCAmeasurement value is denoted by E_(k), then E_(k)<=TL_(k)=−73dBm/MHz+23−PH_(k).

Hereinafter one example is given to describe the above method of thepresent disclosure.

For the downlink direction, suppose that the signals in one channeloccupancy time period are divided into three types, i.e., signals fortransmitting downlink data, signals for transmitting merely DRS andsignals for transmitting merely NZP CSI-RS, A CCA threshold level isconfigured for each type of signals respectively.

When downlink data is to be transmitted during one channel occupancytime period, since the transmission power of the base station may reachits maximum transmission power, a relatively low CCA threshold level TL₁may be configured. For example, it is possible to define a relativelylow CCA threshold level in advance; or use a CCA threshold levelconfigured by higher layer signaling; or configure the CCA thresholdlevel according to the maximum transmission power of the base stationduring the channel occupancy time; or configure the CCA threshold levelaccording to the maximum transmission power defined by the power classof the base station.

If merely the DRS is to be transmitted during one channel occupancy timeperiod, the required transmission power is relatively low. Therefore, arelatively high CCA threshold level TL₂ may be configured. For example,it is possible to define a relatively high CCA threshold level inadvance; or use a CCA threshold level configured by higher layersignaling; or configure the CCA threshold level according to the maximumtransmission power of the DRS during the channel occupancy time; orobtain the CCA threshold level for transmitting the DRS through adding afirst offset to the CCA threshold level for transmitting the downlinkdata, wherein the first offset may be defined in advance or configuredby higher layer signaling. In fact, the DRS consists of several kinds ofcomponent signals. It is possible to respectively configure a CCAthreshold level for each component signal of the DRS, e.g., PSS/SSS, CRSand NZP CSI-RS, Thus it may be determined whether the corresponding DRScomponent signal can be transmitted according to the corresponding CCAthreshold level.

Similarly, if merely the NZP CSI-RS is to be transmitted during onechannel occupancy time period, the required transmission power is alsorelatively low. Therefore, another relatively high CCA threshold levelTL₃ may be configured. For example, it is possible to configure anotherrelatively high CCA threshold level, or use a CCA threshold levelconfigured by higher layer signaling; or configure the CCA thresholdlevel according to the maximum transmission power of the NZP CSI-RS inthe channel occupancy time; or obtain the CCA threshold level fortransmitting the NZP CSI-RS through adding a second offset to the CCAthreshold level for transmitting the downlink data, wherein the secondoffset may be defined in advance or configured by higher layersignaling.

The above first offset and the second offset may be the same ordifferent. The relationship between the CCA threshold levels TL₂ and TL₃may be determined according to the levels of the transmission powers ofthe DRS and the NZP CSI-RS.

Similarly, for the uplink direction, suppose that the signalstransmitted in one channel occupancy time period are classified intothree types: signals for transmitting uplink data, signals fortransmitting PRACH and signals for transmitting merely the SRS.

If uplink data is to be transmitted in one channel occupancy timeperiod, since the transmission power of the UE may reach its maximumtransmission power, a relatively low CCA threshold level TL₄ may beconfigured. For example, it is possible to predefine a relatively lowCCA threshold level, or use a CCA threshold level configured by higherlayer signaling; or configure a CCA threshold level according to themaximum transmission power of the UE during the channel occupancy time;or determine the CCA threshold level according to the maximumtransmission power configured to the UE; or configure the CCA thresholdlevel according to the maximum transmission power defined by a powerclass of the UE.

If merely the PRACH is to be transmitted during one channel occupancytime period, another CCA threshold level TL₅ may be configured. Forexample, it is possible to define another CCA threshold level inadvance; or use a CCA threshold level configured by higher layersignaling; or configure the CCA threshold level according to the maximumtransmission power of the PRACH during the channel occupancy time; orobtain the CCA threshold level for transmitting the PRACH through addinga third offset to the CCA threshold level for transmitting the uplinkdata, wherein the third offset may be defined in advance or configuredby higher layer signaling. In particular, if the transmission power ofthe PRACH may vary with the transmission times of the PRACH, a differentCCA threshold level may be configured for each PRACH transmission.

If merely the SRS is to be transmitted during one channel occupancy timeperiod, another CCA threshold level TL₆ may be configured. For example,it is possible to define another CCA threshold level in advance, or usea CCA threshold level configured by higher layer signaling; or configurea CCA threshold level according to the maximum transmission power of theSRS during the channel occupancy time; or obtain a CCA threshold levelfor transmitting the SRS through adding a fourth offset to the CCAthreshold level for transmitting the uplink data, wherein the fourthoffset may be defined in advance or configured by higher layersignaling.

The third and fourth offsets may be the same or different. Therelationship between the CCA threshold levels TL₅ and LT₆ may bedetermined according to levels of the transmission powers of the PRACHand the SRS.

Embodiment 4

The LTE system supports uplink and downlink transmission power control.Thus, the transmission powers of the base station and the LTE are bothadjustable. In particular:

For the downlink transmission of the LTE system, the eNB may control itsdownlink transmission power according to the channel status of each UE.For example, for transmission modes 1˜6, the transmission power withrespect to one UE may be controlled via semi-statically configuredparameters PA and PB. For transmission modes 7˜9, the downlinktransmission power with respect to one UE may be adjusted dynamicallysince the data demodulation is based on DMRS. Since different UEs may bescheduled by the eNB in different downlink subframes, the totaltransmission power of different downlink subframes are generallydifferent. Further, inside one subframe, different time-frequencyresources may bear different types of information, therefore thetransmission power of different OFDM symbols may also be different. Forexample, the transmission power of OFDM symbols where CRS exist and thetransmission power of other OFDM symbols may be different. Thetransmission power of OFDM symbols where IP CSI-RS is applied and thetransmission power of other OFDM symbols are also different. In view ofthe above, during one channel occupancy time period, the downlinktransmission power of the LTE base station generally varies in differentsubframes or inside one subframe. In addition, for different channeloccupancy time periods, the downlink transmission power of the LTE basestation is also different.

For the uplink transmission of the LTE system, the UE may activelyadjust the transmission power via open-loop power control, and the basestation may control the transmission power of the UE via close-looppower control. In addition, in case that the power is restricted, the UEmay adjust the transmission power of a component carrier according to acertain criteria. In one uplink subframe, the transmission power of theUE is also variable. For example, PUSCH is transmitted at the start ofone uplink subframe and SRS is transmitted on the last symbol. Thus, theuplink transmission power of the UE is also adjustable.

In one channel occupancy time period, the base station may transmitdownlink data, or transmits merely the DRS, or transmits merely thereference signal used for CSI measurement. According to the abovedescription, in one channel occupancy time period, the LTE equipment maytransmit preamble at the start of the channel occupancy time. In onechannel occupancy time period, the transmission power of the LTEequipment is fluctuate. The variation of the transmission power of theequipment actually affects the CCA check of other adjacent equipment.When the transmission power of the equipment is relatively high,equipment in a large area around the equipment may observe that thechannel is occupied; whereas when the transmission power of theequipment is relatively low, merely equipment in a relatively small areaaround the equipment may observe that the channel is occupied. Supposethat during the channel occupancy time, the first equipment transmitsdata with a relatively low transmission power first. Thus the equipmentat a certain distance from the first equipment may start to transmitsignals since its CCA check indicates that the channel is idle. When thefirst equipment increases its transmission power during the latter partof the channel occupancy time, interference will be generated to theother equipment. In order to avoid this situation, the presentdisclosure provides a processing method. Hereinafter, the OFDM symbolsrefer to OFDM symbols of downlink subframes and SCFDMA symbols of uplinksubframes.

In a first method, in one channel occupancy time period, it is requiredthat the transmission power on each OFDM symbol is fixed or is decreasedwith time.

Since the transmission power on different OFDM symbols in one LTEsubframe are usually different. In the second method, in one channeloccupancy time period, it is required that the average transmissionpower of each subframe is fixed or is decreased with time. As shown inFIG. 6, in one channel occupancy time period, the average transmissionpower of each subframe is decreased with time. Herein, it may be furtherrequired that the difference between the transmission powers ondifferent OFDM symbols in one subframe is within a certain range. Therange of the difference between the transmission powers may be definedin advance by standards or configured by signaling or other methods.

In a third method, in one channel occupancy time period, the differencebetween the transmission powers on different OFDM symbols is required tobe within a certain range. As shown in FIG. 7, in the LTE system, it maybe not ensured that the transmission powers on all OFDM symbols arecompletely consistent. But it is possible to define that the differencebetween the transmission powers on different OFDM symbols has to bewithin a certain range. The range of the difference between thetransmission powers may be defined by standards in advance, orconfigured by signaling or other methods.

In a fourth method, in one channel occupancy time period, it is requiredthat the difference between the transmission powers on different OFDMsymbols in one subframe is within a first range, and it is furtherrequired that a difference between the average transmission powers ofdifferent subframes during the channel occupancy time is within a secondrange. The above two ranges may be defined by standards in advance, orconfigured by signaling or other methods. In particular, the two rangesmay be the same. Thus it is only required to configure one parameter forthe variation range of the transmission powers.

In the above method, suppose that merely a part of a subframe is withinthe channel occupancy time. The average transmission power of thesubframe refers to the average transmission power of the part within thechannel occupancy time.

Embodiment 5

On a channel of the unlicensed band, in the CCA-based channel statusdetecting method, if the transmission power of the equipment may be keptunchanged during the channel occupancy time, it is more favorable forcoexistence with other equipment.

For the downlink transmission of the LTE system, in order to increasethe measurement accuracy ratio of the adjacent cell CSI-RS or to provideinterference measurement resource (CR-IM), ZP CSI-RS may be configuredin one subframe, which may result in decrease of the transmission powerof the equipment on the OFDM symbols of the ZP CSI-RS. For example,suppose that a ZP CSI-RS resource is configured, equivalent to transmitno signal on one subcarrier of every 6 subcarriers, which results in adecreases of 16.7% in the transmission power.

In one embodiment, in order to ensure a stable transmission power asmuch as possible, in the present disclosure, power boosting is performedto the PDSCH of the user in the OFDM symbols containing ZP CSI-RS.

In a first method, a power boosting proportion of the PDSCH on the OFDMsymbols containing ZP CSI-RS is configured by higher layer signaling.The signaling may be transmitted with respect to each UE or transmittedto each cell via broadcast signaling. Herein, since the ZP CSI-RS may beconfigured on multiple different positions of the subframe, a powerboosting proportion may be configured for the PDSCH on each pair of OFDMsymbols which may contain the ZP CSI-RS respectively; or, a single powerboosting proportion may be configured, which is applicable for thetransmission of the PDSCH on all OFDM symbols which may contain the ZPCSI-RS.

In a second method, the UE calculates a PDSCH power boosting proportionon PRB resources allocated to the UE according to the ZP CSI-RSconfiguration. Suppose that ZP CSI-RS is configured on k subcarriers ofone PRB of one OFDM symbol. When PDSCH is transmitted on the other N−ksubcarriers, the power boosting proportion may be Ni(N−k), wherein N isthe number of subcarriers in the PRB and N=12. In one subframe,different UEs may be configured with different ZP CSI-RS, which mayresult in different power increases of the PDSCH.

In the above method, through the power boosting of the PDSCH on the OFDMsymbols where the ZP CSI-RS is applied, the difference betweentransmission powers on different OFDM symbols may be reduced as much aspossible. This method also has its deficiency. For example, if the ZPCSI-RS is applied to all subcarriers in one PRB of one OFDM symbol, theabove method is unable to address the power difference on the OFDMsymbols where the ZP CSI-RS is applied. Therefore, on the unlicensedband, it may be defined that in the frequency range of one PRB, thenumber of subcarriers used for ZP CSI-RS does not exceed a threshold K,so as to ensure that there is a subcarrier within the PRB on whichsignals are transmitted. If it is required to ensure that a subcarrieron which signals are transmitted exists in each 100 kHz, it may bedefined that K is larger than or equal to 2, and the two subcarrierswhich are not used for ZP CSI-RS are distributed in one PRB, e.g., theindex interval of the two subcarriers is 6. The value of K may bedefined in advance by standards or configured by signaling or othermethods.

Embodiment 6

On one channel of the unlicensed band, according to the EuropeanRegulations, the equipment shall occupy 80%˜100% of the bandwidth whentransmitting signals, which conflicts with the frequency resourceallocation based on PRBs of the LTE system. In fact, in the LTE system,for a 20 MHz system bandwidth, the number of PRBs allocated in onesubframe may vary between 0 and 100. In the LTE system, even if thelowest MCS level is considered, when 80 PRBs are allocated to the UE,the Transmission Block Size (TBS) still reaches 2216 bits. Under aparticular condition, if merely a minimum TBS of 2216 bits is supportedby one channel of the unlicensed band, system flexibility is restricted.According to the above analysis, under the particular condition, the LTEbase station cannot transmit effective data on at least 80% bandwidth.At this time, the base station needs to transmit dummy signals so as tomeet the requirement of the European Regulations.

According to the DRS structure of LTE Rel. 12, the DRS includesPSS/SSS/CRS, and may be configured to further include CSI-RS. Thesesignals of the DRS are mapped on non-consecutive OFDM symbols. In orderto prevent other equipment start from transmitting signals between theOFDM symbols where the DRS is mapped, the base station also need totransmit dummy signals to keep the channel occupied. The dummy signalsmay be transmitted on OFDM symbols on which no PSS/SSS/CRS/CSI-RS ismapped of the subframe containing the DRS; or, the dummy signals mayalso be transmitted on all OFDM symbols of the subframe containing theDRS. For the subframe containing the DRS, if no downlink data isscheduled, dummy signals may be transmitted in all PRBs or 80% of thePRBs of the whole system bandwidth. For the subframe containing the DRS,after the filling of the dummy signals, signals are transmitted onconsecutive carriers of the OFDM symbols or on some subcarriers of theOFDM symbol. The subcarrier pattern for mapping the dummy signals may beconfigured in advance or configured by higher layer signaling.

The transmission power of the dummy signals cannot be too low; otherwisethe effect of occupying the channel cannot be realized. The transmissionpower of the dummy signals cannot be too high; otherwise it affects thereceiving of signals on effective PRBs of the UE. In the presentdisclosure, an Energy Per Resource Element (EPRE) of the dummy signalsis lower than or equal to a minimum value of the EPRE on effective PRBs.The degree that the EPRE of the dummy signals is lower than the minimumvalue of the EPRE on the effective PRBs may be defined in advance, orconfigured by signaling or other methods, or is relevant to animplementation. Or, the EPRE of the dummy signals may be higher than theminimum value of the EPRE on the effective PRBs. But the excess islimited. The excess may be defined in advance, or configured bysignaling or other methods, or is relevant to a practical application.

In the LTE system, Network Assisted Interference Cancellation andSuppression (NAICS) technique is supported to improve performance of areceiver. That is, the receiver needs to detect characteristic of theinterference signals and try to eliminate the impact of the interferencesignals. Considering the requirement of the NAICS, the presentdisclosure provides a following method for designing the dummy signals.

In one PRB pair containing the dummy signals, signals are transmitted onREs of DMRS following the generation manner of the DMRS, such that theUE performing the NAICS is able to perform channel estimation based onthe DMRS of the dummy signals. Herein, the sequence parameters of theDMRS of the dummy signals, e.g., cell ID and n_(scid) may be defined inadvance; or may be configured to the NAICS UE by higher layer signaling.For the NAICS UE, the above cell ID and n_(scid) may be the same with acell ID and n_(scid) used for assisting the interference cancellation,or may be independent parameters. In other words, it is possible to addconfiguration information of the DMRS of the dummy signals into existinginterference DMRS configuration signaling. Or, the existing interferenceDMRS configuration signaling may be reused, such that the base stationadopts the corresponding DMRS when transmitting the dummy signals. Incase that the dummy signals are configured with dedicated DMRS, then_(scid) may be an integer except for 0, 1 and 2, e.g., n_(scid)=3.Thus, the DMRS sequence of the dummy signals is different from that ofthe PDSCH and the EPDCCH.

In one PRB pair containing the dummy signals, the data REs of the PDSCHmay merely adopt a QPSK modulation to obtain better NAICS performance.Herein, the QPSK modulation symbols born by each RE are random. Or,known QPSK sequences are transmitted on each RE of the PRB paircontaining the dummy signals. Suppose that the PRB pair containing thedummy signals may be recognized through the DMRS detection of the PRBpair wherein the dummy signals are located, the UE may completely cancelthe above known QPSK sequence, so as to further improve the performanceof the NAICS. The EPRE of the DMRS of the dummy signals and the EPRE onthe data REs of the dummy signals may be the same or have a fixed ratio,wherein ratio may be configured by higher layer signaling.

In one PRB pair containing the dummy signals, in order to obtain betterNAICS performance, it is possible to transmit the dummy signals of asingle antenna port. Suppose that the dummy signals are generatedfollowing the method based on the transmission mode of the CRS. Aprecoding method is adopted to transmit the dummy signals of merely oneantenna port. The precoding matrix of the dummy signals may be definedin advance or configured by higher layer signaling. For the transmissionmode of the CRS, the dummy signals may be transmitted according to afixed power control parameter (PA), e.g. a minimum PA value allowed bythe LTE standards, or the PA value may be defined in advance orconfigured by higher layer signaling. Or, the dummy signals may betransmitted using a value smaller than the minimum PA value defined bythe current standards, wherein the PA value may be defined in advance orconfigured by higher layer signaling.

In order to improve the NAICS performance and decrease the complexity,one NAICS UE processes merely interference signals of merely one orseveral transmission modes. Thus, in one PRB pair containing the dummysignals, when the dummy signals are transmitted, a transmission modethat the interfered NAICS UE is able to detect and eliminate needs to beadopted to transmit the dummy signals.

In accordance with the above method, an apparatus for transmitting datais provided by the present disclosure. As shown in FIG. 9, the apparatusincludes: a detecting module and an occupation module; wherein,

the detecting module is adapted to perform a CCA in one channel of theunlicensed band;

the occupation module is adapted to determine whether the channel can beoccupied according to a CCA measurement value in the channel, anddetermine data transmission parameter if the channel can be occupied.

In one embodiment, when determining the data transmission parameter, theoccupation module is further adapted to: take the CCA measurement valueas a first CCA threshold level, obtain a maximum transmission powerallowed during a next channel occupancy time according to a relationshipbetween the first CCA threshold level and the maximum transmissionpower.

In one embodiment, when determining whether the channel can be occupied,the occupation module is further adapted to: perform the operation ofdetermining the data transmission parameter to determine the maximumtransmission power if the CCA measurement value is lower than a secondCCA threshold level, and do not occupy the channel if the CCAmeasurement value is equal to or higher than the second CCA thresholdlevel.

In one embodiment, the detecting module is further adapted to record CCAmeasurement values during the CCA; and

when determining the data transmission parameter, the occupation moduleis further adapted to: take a maximum value among N smallest CCAmeasurement values as the first CCA threshold value according to the CCAmeasurement values recorded by the detecting module, and obtain themaximum transmission power allowed during the next channel occupancytime according to the relationship between the first CCA threshold leveland the maximum transmission power; or,

when performing the CCA, the detecting module is further adapted to:record N smallest CCA measurement values up to present; when determiningthe data transmission parameter, the occupation module is furtheradapted to: take the maximum value among the N smallest CCA measurementvalues as the first CCA threshold level, and obtain the maximumtransmission power allowed during the next channel occupancy timeaccording to the relationship between the first CCA threshold level andthe maximum transmission power; or,

when performing the CCA, the detecting module is further adapted to:obtain the first CCA threshold level according to a required maximumtransmission power, and detect the channel according to the first CCAthreshold level, when the CCA check indicates that the number of timesthat the channel is idle reaches N, the occupation module occupies thechannel.

In one embodiment, when performing the CCA, the detecting module doesnot record the CCA measurement value if the CCA measurement value isequal to or higher than the second CCA threshold level.

In one embodiment, the detecting module is further adapted to obtain CCAmeasurement values of at least two types of signals when performing theCCA;

when determining the data transmission parameter, the occupation moduleis further adapted to: respectively take the CCA measurement value ofeach type of signals as the first CCA threshold level, determine acorresponding allowed maximum transmission power according to therelationship between the first CCA threshold value and the maximumtransmission power; wherein the maximum transmission power of theequipment allowed during the next channel occupancy time is a minimumvalue of the allowed maximum transmission powers of the at least twotypes of signals.

In one embodiment, the CCA measurement values of at least two types ofsignals include: an energy density of recognizable signals from the LTEsystem and an energy density of the signals from other systems; or,

the CCA measurement values of the at least two types of signals include:energy of recognizable signals from an LTE system of the same operatorwith the LTE equipment, energy of recognizable signals from an LTEsystem of an operator different from the LTE equipment and energy ofother signals.

In one embodiment, the allowed maximum transmission power is a maximumvalue of transmission powers on OFDM symbols or SCHWA symbols during thechannel occupancy time; or

the allowed maximum transmission power is a maximum value of averagetransmission powers of subframes during the channel occupancy time; or

the allowed maximum transmission power is a maximum value of an instanttransmission power during the channel occupancy time.

In one embodiment, the CCA threshold level is determined according tothe type of signals to be transmitted in the channel, if the CCAmeasurement value is lower than the CCA threshold value, the equipmentoccupies the channel to transmit the signals of the type.

In one embodiment, the transmission power on each OFDM symbol isunchanged or decrease with time during the channel occupancy time.

In one embodiment, the difference between transmission powers ondifferent OFDM symbols of one subframe is within a predefined range.

In one embodiment, during one channel occupancy time, the differencebetween the transmission powers on different OFDM symbols is within apredefined range; or

during one channel occupancy time, the difference between thetransmission powers on different OFDM symbols in a subframe is within afirst range, and the difference between average transmission powers ofdifferent subframes is within a second range.

In one embodiment, the occupation module is further adapted to obtain apower boosting proportion of a Physical Downlink Shared Channel (PDSCH)on OFDM symbols containing Zero power Channel State Indication-ReferenceSignal (LP CSI-RS) according to higher layer signaling; or

the occupation module is further adapted to calculate a power boostingproportion of the PDSCH on PRBs allocated to the apparatus according tothe configuration of ZP CSI-RS.

In one embodiment, the apparatus further transmits dummy signals.

In one embodiment, the EPRE of the dummy signals is equal to or lowerthan a minimum value of the EPRE on effective PRBs.

In one embodiment, in one PRB pair containing the dummy signals, theDMRS sequence is defined in advance, or is configured to the NAICS UEvia higher layer signaling.

In one embodiment, if dedicated DMRS is configured for the dummysignals, n_(scid) is equal to an integer except for 0, 1, and 2.

In one embodiment, in one PRB pair containing the dummy signals, a QPSKmodulation manner is adopted on data REs of the PDSCH, and the QPSKmodulation symbol born by each RE is random; or a known QPSK sequence istransmitted on each RE of the PRB pair.

In one embodiment, in one PRB pair containing the dummy signals, dummysignals of a single antenna port are transmitted.

In one embodiment, for a transmission mode based on the CRS, a precodingmatrix of the dummy signals is defined in advance or configured byhigher layer signaling.

In one embodiment, for the transmission mode based on the CRS, the dummysignals are transmitted using a minimum power control parameter PA,wherein the PA is defined in advance or configured by higher layersignaling.

The foregoing descriptions are only preferred embodiments of thisdisclosure and are not for use in limiting the protection scope thereof.Any changes and modifications can be made by those skilled in the artwithout departing from the spirit of this disclosure and thereforeshould be covered within the protection scope as set by the appendedclaims.

What is claimed is:
 1. A method performed by a base station in awireless communication system, the method comprising: determining atleast one energy detection threshold for sensing based on a signal to betransmitted; identifying a detected power corresponding to a channel ofan unlicensed band; determining whether the channel is idle based on thedetected power and the at least one energy detection threshold; andtransmitting the signal to a user equipment (UE) on the channel based ona determination that the channel is idle, wherein the at least oneenergy detection threshold corresponds to the signal to be transmittedincluding a first signal or a second signal, and wherein the secondsignal includes at least one discovery signal, and the first signal isdifferent from the second signal.
 2. The method of claim 1, whereindetermining whether the channel is idle based on the detected power andthe at least one energy detection threshold comprises: identifyingwhether the detected power for a predetermined time period is less thanthe at least one energy detection threshold; and determining that thechannel is idle in case that the detected power is less than the atleast one energy detection threshold.
 3. The method of claim 1, whereinthe first signal includes a downlink data.
 4. The method of claim 1,wherein determining the at least one energy detection thresholdcomprises: determining at least one energy detection threshold based ona value corresponding to the signal and a fix value corresponding to 23.5. The method of claim 1, wherein the at least one discover signalincludes primary synchronization signal (PSS) and secondarysynchronization signal (SSS).
 6. The method of claim 1, wherein the atleast one energy detection threshold corresponding to the first signalis different from the at least one energy detection thresholdcorresponding to the second signal.
 7. A base station in a wirelesscommunication system, the base station comprising: a transceiver; and atleast one processor coupled with the transceiver and configured to:determine at least one energy detection threshold for sensing based on asignal to be transmitted, identify a detected power corresponding to achannel of an unlicensed band, determine whether the channel is idlebased on the detected power and the at least one energy detectionthreshold, and transmit the signal to a user equipment (UE) on thechannel based on a determination that the channel is idle, wherein theat least one energy detection threshold corresponds to the signal to betransmitted including a first signal or a second signal, and wherein thesecond signal includes at least one discovery signal, and the firstsignal is different from the second signal.
 8. The base station of claim7, wherein the at least one processor is configured to: identify whetherthe detected power for a predetermined time period is less than the atleast one energy detection threshold, and determine that the channel isidle in case that the detected power is less than the at least oneenergy detection threshold.
 9. The base station of claim 7, wherein thefirst signal includes a downlink data.
 10. The base station of claim 7,wherein the at least one processor is configured to determine at leastone energy detection threshold based on a value corresponding to thesignal and a fix value corresponding to
 23. 11. The base station ofclaim 7, wherein the at least one discover signal includes primarysynchronization signal (PSS) and secondary synchronization signal (SSS).12. The base station of claim 7, wherein the at least one energydetection threshold corresponding to the first signal is different fromthe at least one energy detection threshold corresponding to the secondsignal.